$A$ vessel of $2.461 \ L$ contains a mixture of $0.3 \ mol$ of $N_2$,$0.5 \ mol$ of $He$,and $6.2 \ mol$ of $O_2$ at $27 \ ^oC$. What is the partial pressure of $N_2$ in the mixture in $atm$?

The unit of pressure is equivalent to which of the following?

Cooking is fast in a pressure cooker,because

If the rate of diffusion of $A$ is $5$ times the rate of diffusion of $B$,what will be the ratio of the densities of $A$ and $B$?

Write the formula for partial pressure.

Fill in the blanks:
$(1)$ The properties of gases were first measured by ......... .
$(2)$ The dipole-dipole interaction energy between stationary polar molecules is proportional to .......... .
$(3)$ The interaction energy between rotating polar molecules is proportional to .......... .
$(4)$ The bond energy of a hydrogen bond is about ......... $kJ \ mol^{-1}$.